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gtoonstra edited this page Jun 12, 2015 · 6 revisions

Orthomosaics and DEM's

Here's a list of tools that are capable of producing orthomosaics and DEM's:

Tip 1 When you export the orthomosaic and the DEM from the photogrammetry software for GIS purposes, try to export them with a UTM projection and annotate the filename with the datum, projection and utm zone. The datum is for example WGS84, SAD69, NAD27 or whatever. The UTM is a projection of the datum in use onto a grid where x,y and z become 1 meter per unit.

The file always stores whatever unit you use for the coordinates in their native unit, so if you use degrees, then you get much smaller numbers. Some softwares are unable to project/convert these units directly, so then you may get strange results in volumetric calculations and other operations involving the extra Z component (slope, hillshade, etc). This happens because the Z axis is in a totally different unit. Pay attention: may, your software may work fine.

UTM is such a projection, but it is important to indicate if the data was derived from a WGS84 datum and for completeness, indicate the UTM zone you used for the projection.

Example: dem_surveyx_wgs84_utm25s.tif

For more info on UTM, see here and here.

Tip 2

When you export data to a TIFF and you are using this for radiometric measurements, you don't want to use "color correction", because this messes up your NIR and RGB measurements.

Tip 3

Before processing, review your project settings. There are usually settings there related to the number of keypoints extracted from a picture, the number of tie points required (points involved in confirmed matches), the considered precision for GCP's, the considered precision for camera GPS. If those settings are incorrect, then your model may not be complete, you get unmatched photos, etc.

Tip 4

Higher quality runs produce significantly better results, especially if your dense cloud uses more points. It significantly improves the quality of the height map for example.

Multispectral data (RGB/NIR)

  • Pix4D
  • Agisoft Photoscan
  • DroneMapper ...

Meteorological data

...

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